/Engine/Source/Runtime/Slate/Public/Widgets/Layout/SMenuOwner.h
Any widget that wants to own lists of items that may have sub-menus that should be handled in the same way as multibox menus (mouse can cross other items without sub-menu closing)
class SMenuOwner : public [SCompoundWidget](API\Runtime\SlateCore\Widgets\SCompoundWidget)
TWeakPtr<SMenu...
SummonedMenuAnchor
For menu bar widgets, this stores a weak reference to the last pull-down or sub-menu that was summoned.